The invention concerns a method and apparatus for reclaiming a relatively high-boiling heat treating salt from the rinsing bath of heat treating units wherein the heat treating bath contains a molten heat treating salt at an elevated temperature.
When metal articles are quenched, hardened or otherwise treated in a heat treating bath in the course of a heat treating process and are thereafter washed in a rinse bath a certain quantity of the heat treating salt is carried along by the metal parts from the heat treating bath into the rinsing tank. As a consequence the rinse water in time becomes richer in its content of heat treating salt. It is the purpose of this invention to remove this salt content from the wash water tank and to reclaim the heat treating salt for the heat treating bath.
For heat treating baths which comprise a mixture of heat treating salt with a certain quantity of water, devices are known which return rinse water to the heat treating bath for the purpose of maintaining the desired water content of the heat treating bath by adding it to the mixture of heat treating salt and water contained in the salt bath. In doing this the heat treating salt contained in the rinse water is returned into the molten salt bath simultaneously with the rinse water. This type of method is useful in reclaiming heat treating salt from the wash water tank and returning it to the molten salt tank only when rinse water is intended to be added to the heat treating or quench bath for the purpose of maintaining the desired water content thereof. See, for instance, U.S. Pat. No. 2,537,830 (Holden); U.S. Pat. No. 2,931,745 (Halgren) and U.S. Pat. No. 3,645,802 (Keough). This method of reclaiming heat treating salt, however, cannot be used for such heat treating baths which do not consist of an aqueous heat treating salt mixture but only of a substantially anhydrous hot heat treating salt in its molten state.
It is therefore the purpose of this invention to make it possible in the case of heat treating units of the type which comprise a salt bath consisting essentially only of a molten heat treating salt, to reclaim in a simple and economic manner the salt content from the rinse water of the wash water tank without a constant renewal of the rinse bath and to reclaim the heat treating salt which had been carried into the wash water tank back to the heat treating bath.